Voice signal power amplifier.

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gar

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160715-2139 EDT

Who invented the first voice signal power amplifer, and how does a signal power amplifier work? Why was this invention important? Note conservation of energy does not allow creation of power from nowhere.

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Is this a trivia question? My answer would be Western Electric who made repeater amps that made long distance and transoceanic service possible. Yes they were vacuum tube and powered.

-Hal
 
I see your point !
Don,t think the last poster did thou.
Being strictly pedantic,
Of course there is no such thing as a "power amplifier"
There is of course voltage amplifiers and current amplifiers,
But you cannot have both at the same time.

:thumbsup:
 
160715-2446 EDT

zbang:

The first audio-frequency amplifier of any kind was probably the megaphone.
Click to expand...
I would classify this as a power concentrator, but not a power amplifier.

The triode vacuum tube can be a power amplifier of a voice signal, or other signal. It is a modulator of some power source. The voice signal output of the triode can be much greater than the voice power input. Watts output from milli or microwatts input.

The answer I am looking for predates the triode.

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gar said:
160715-2446 EDT

zbang:

I would classify this as a power concentrator, but not a power amplifier.

The triode vacuum tube can be a power amplifier of a voice signal, or other signal. It is a modulator of some power source. The voice signal output of the triode can be much greater than the voice power input. Watts output from milli or microwatts input.

The answer I am looking for predates the triode.

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Click to expand...
Are you looking for the carbon granule microphone (a transducer whose electrical power output is greater than the mechanical power input.)
Or go back a bit earlier to the acid-dipped-wire transducer that Bell first used?

Did anyone ever make a pneumatic amp where voice sound pressure modulated the flow of pumped air (variant on organ pipe, or maybe kazoo?)

If you do not restrict it to voice, maybe whip and horse or lure and ox combination in biblical? times. A mechanical to mechanical amplifier.
 
169716-0822 EDT

GoldDigger:

Good reply. I used the wording "voice signal" to imply several things. A moderately linear amplifier, and to exclude talk about perpetual motion and "bang-bang" amplifiers. Kicking a horse would be a sort of "bang-bang" amplifier. The purpose of the question was to provoke thought and research.

A triode tube type amplifier has a somewhat linear transfer function from input to output if operated in a restricted region. Thus, output signal power is quite a bit less than the total power input to the amplifier. To operate class A, linear, causes a lot of plate heat loss. To this has to be added the heater power (filament). Plate power loss can be reduced by going to class B operation, but then a push-pull circuit is needed to get approximately linear operation.

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Who invented ..first voice signal power amplifer

Simple answer: Thales, circa 600 BC.

If you take away the word 'power' and simply use amplitude, then the first person to ever put their hand behind their eat to hear better.
 
160716-1540 EST

hbiss:

The intent of my original post was to start a discussion. I was thinking of telephone communication. But there is no reason that should be a restriction on thought.

I do not think of a megaphone as an amplifier. But I think I would call a hand cupped at my ear or a telescope lens a power amplifier because these collect energy from a broader area and concentrate that energy at a smaller area.

GoldDigger:

I was thinking of the carbon microphone. I have no absolute answer to my question.

If I had not used voice in the problem, then many binary operations could be considered amplifiers. Smoke signals for one.

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Telephone communication was my first thought also. However I would not consider a carbon microphone (or any kind of microphone) as an amplifier. It just converts one kind of energy into another.

-Hal
 
1607162258 EDT

On searching I found a very interesting article that is probably correct in many respects. I somewhat question the time sequence information for microphones in the 1930 to mid 1940 time frame.

See http://microphone-data.com/media/filestore/articles/History-10.pdf

Radios of the 1920s and early 1930s used electromagnets for the speaker. I have a couple different radios with such speakers. I have a radio from 1940 with a permanent magnet speaker. Also bought a cheap microphone in 1942 that used a small PM speaker, 2" diameter, for the microphone.

Alnico was invented in 1932. See

http://link.springer.com/article/10.1007/BF03220870#page-1
You must click on "look inside" to see the article.

My first exposure to broadcast microphones was in 1936. I don't know what was in side. But speach quality was quite good by this time and probably better by 1940.


hbiss:

It is quite common to talk about power amplification in the communication world. A carbon microphone is truely a power amplifer from the standpoint of the input accoustic signal to the microphone to the electrical signal power output. There is a very large multiplying factor here, and that is why the telephone industry was able to develop into a viable industry.

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gar said:
1607162258 EDT
used electromagnets for the speaker
Click to expand...

humbucker :roll:





betcha most the young whippersnappers would not believe an 8 pound coil of 38 AWG, eh :D

BTW, I did not know Thales personally :lol:
 
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The electromagnets (used to produce the field against which the voice coil acts) often double as the input choke in the DC power supply, so not wasting as much energy as you might think.
If the speaker had been good enough to reproduce 120 or 60Hz audio the hum would have been annoying..
 
hum would have been annoying

That is why there was a 'humbucker' coil also.

Tens of thousands of turns of small wire with 500Vdc around 10 mA or so and associated ripple, then a separate winding of a few turns of 12 or 14 AWG in series with the 6V tube filaments to 'buck' the 60Hz core flux.
 
gar said:
Also bought a cheap microphone in 1942 that used a small PM speaker, 2" diameter, for the microphone.
Click to expand...
There are kick drum microphones made today that use a speaker (8" or so) to pick up the sound.

When I was in (what is now called) middle school I made an electric guitar by taping a 4" speaker over the sound hole of my cheap Silvertone acoustic guitar and running wires from the terminals to the phono inputs of an old tube radio/phonograph combo. It sounded awful, but on the positive side, I discovered distortion and feedback. :D
 
160717-1314 EDT

I was not aware of any "hum bucking" coils. There would be no object in bucking 60 Hz since the ripple fundamental frequency is 120 hz. Thus, filament supply current could not be used directly.

An interesting article is http://www.edisontechcenter.org/speakers.html . My 1928 GE superheterodyne, two TRF stages, has an electromagnet speaker. I believe that speaker would reproduce 60 Hz.

The following article is quite wrong in timing, and somewhat wrong in other ways. https://en.wikipedia.org/wiki/Electrodynamic_loudspeaker

This next article has some useful information, but again timing is wrong. I have a Utah speaker from just before WWII with an Alnico magnet. Speakers as such were readily available. https://en.wikipedia.org/wiki/Loudspeaker

Google as a useful search engine is getting quite bad. I have not found a reference to a hum bucking coil.

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